- Perimeter of a closed figure is the distance around it while area is the measure of the part of plane or region enclosed by it.
- Perimeter of a regular polygon = Number of sides × Length of one side.
- Perimeter of a square = 4 × side
- Perimeter of a rectangle = 2(l + b)
- Area of square = side × side
- Area of rectangle = l × b
- Area of parallelogram = b × h
- Area of triangle = 1 / 2 ×b×h
- The distance around a circle is known as its circumference.
- The ratio of circumference and diameter of a circle is a constant and is denoted by π (pi).
- Approximate value of π is taken as 22 / 7 or 3.14
- Circumference of a circle of radius r is 2πr,
- Area of a circle of radius r is πr2.

**Circumference Of Circle**

**Words**

The circumference C of a circle is π times the diameter d, or 2π times the radius r.

**Numbers**

C = π × 6

= 2π × 3

= 18.8 units

**Formula**

C = πd

or

C = 2πr

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